How to remove and to reinstall IIS on a computer that is running Exchange Server

http://support.microsoft.com/kb/320202

So in a nut shell for E2k7 on W2K3: uninstall IIS, and reinstall and then patch the OS.

uninstall the CAS role, and reinstall the case role.

setup /role:ca /mode:uninstall
setup /role:ca /mode:install

then recreate the VDir's from the Exchange management shell.